In a letter to all MPs, Dr Healy said a plebiscite on same-sex marriage would bring about hurtful and divisive commentary under the guise of fair debate.

“The ‘no’ side posters which declared that ‘every child deserves a mother and a father’ were deeply hurtful and upsetting for LGBT-headed families as they passed the posters on lamp posts and billboards across the country – explaining to our children that they were OK and trying to hide the posters from them was awful for LGBT parenting families.

“Likewise, some LGBT canvassers who were out asking for rights for themselves suffered greatly from the hateful comments they heard on doorsteps and in train or bus stations while canvassing.” Dr Healy warned MPs not to underestimate how damaging the campaign ahead of a vote, now expected in February, could be.